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    Subject[PATCH v2 2/6] x86, mm, pat: Change reserve_memtype() to handle WT
    Date
    This patch changes reserve_memtype() to handle the WT cache mode.
    When PAT is not enabled, it continues to set UC- to *new_type for
    any non-WB request.

    When a target range is RAM, reserve_ram_pages_type() fails for WT
    for now. This function may not reserve a RAM range for WT since
    reserve_ram_pages_type() uses the page flags limited to three memory
    types, WB, WC and UC.

    Signed-off-by: Toshi Kani <toshi.kani@hp.com>
    ---
    arch/x86/include/asm/cacheflush.h | 4 ++++
    arch/x86/mm/pat.c | 16 +++++++++++++---
    2 files changed, 17 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
    index 157644b..c912680 100644
    --- a/arch/x86/include/asm/cacheflush.h
    +++ b/arch/x86/include/asm/cacheflush.h
    @@ -53,6 +53,10 @@ static inline void set_page_memtype(struct page *pg,
    case _PAGE_CACHE_MODE_WB:
    memtype_flags = _PGMT_WB;
    break;
    + case _PAGE_CACHE_MODE_WT:
    + case _PAGE_CACHE_MODE_WP:
    + pr_err("set_page_memtype: unsupported cachemode %d\n", memtype);
    + BUG();
    default:
    memtype_flags = _PGMT_DEFAULT;
    break;
    diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
    index 598d7c7..7644967 100644
    --- a/arch/x86/mm/pat.c
    +++ b/arch/x86/mm/pat.c
    @@ -268,6 +268,8 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)

    /*
    * For RAM pages, we use page flags to mark the pages with appropriate type.
    + * The page flags are currently limited to three types, WB, WC and UC. Hence,
    + * any request to WT or WP will fail with -EINVAL.
    * Here we do two pass:
    * - Find the memtype of all the pages in the range, look for any conflicts
    * - In case of no conflicts, set the new memtype for pages in the range
    @@ -279,6 +281,13 @@ static int reserve_ram_pages_type(u64 start, u64 end,
    struct page *page;
    u64 pfn;

    + if ((req_type == _PAGE_CACHE_MODE_WT) ||
    + (req_type == _PAGE_CACHE_MODE_WP)) {
    + if (new_type)
    + *new_type = _PAGE_CACHE_MODE_UC_MINUS;
    + return -EINVAL;
    + }
    +
    if (req_type == _PAGE_CACHE_MODE_UC) {
    /* We do not support strong UC */
    WARN_ON_ONCE(1);
    @@ -328,6 +337,7 @@ static int free_ram_pages_type(u64 start, u64 end)
    * - _PAGE_CACHE_MODE_WC
    * - _PAGE_CACHE_MODE_UC_MINUS
    * - _PAGE_CACHE_MODE_UC
    + * - _PAGE_CACHE_MODE_WT
    *
    * If new_type is NULL, function will return an error if it cannot reserve the
    * region with req_type. If new_type is non-NULL, function will return
    @@ -347,10 +357,10 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
    if (!pat_enabled) {
    /* This is identical to page table setting without PAT */
    if (new_type) {
    - if (req_type == _PAGE_CACHE_MODE_WC)
    - *new_type = _PAGE_CACHE_MODE_UC_MINUS;
    + if (req_type == _PAGE_CACHE_MODE_WB)
    + *new_type = _PAGE_CACHE_MODE_WB;
    else
    - *new_type = req_type;
    + *new_type = _PAGE_CACHE_MODE_UC_MINUS;
    }
    return 0;
    }

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